The fundamental hypothesis on which these studies is based is that non-collagenous proteins (NCPs) of mineralized connective tissues are involved in the formation of the tissues. The mechanism of their involvement in dentinogenesis is unknown, but several studies indicate that NCPs are made by odontoblasts and are secreted at the mineralization front, suggesting that they might be involved in the transformation of predentin to dentin. In this grant application we propose to study the nature and biosynthesis of NCPs of dentin. For biosynthesis we have devleoped a rat molar tooth organ culture system that will mineralize in vitro when cultured in the presence of serum, but does not mineralize in its absence. With this system we will study the biosynthesis and secretion of NCPs relative to mineralization. The effects of 1,25-dihydro0xyvitamin D3 on the synthesis of dentin Gla proteins by molar organs will be investigated to determine if receptors for the hormone are present in odontoblasts. Using antibodies raised against purified NCPs immunolocalization studies will be performed to determine the cell and tissue location and to study the developmental appearance. These experiments will bring about a further understanding of the fundemental biochemical mechanisms involved in the formation of dentin. This information will be useful in understanding the basic causes of certain genetic and systemic diseases that affect mineralized tissues. Fundamental research of this type will ultimately be useful in planning preventive and treatment procedures for mineralized tissue diseases.